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Mathematical formulas such as 
$c^2=a^2+b^2$ 
may be printed in-text just like here,
or they may be printed as displayed formulas such as the following:
\[c^2=a^2+b^2\]
Displayed formulas may have an automatically generated equation number:
\begin{equation}c^2=a^2+b^2\label{ff1}\end{equation}
to which you can even refer by means of 
\verb:\label{...}: and \verb:\ref{...}: commands (this is formula~\ref{ff1}).
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